1. Field of the Invention
The invention relates in general to a system for cleaning and etching wafers, and more particularly to a system for cleaning and etching, that does not need to clamp wafers frequently and saves space.
2. Description of the Related Art
Wet etching is the earliest etching technique that has been used. It removes thin film that is not covered by photoresist, using the chemical reaction between the thin film and a chemical solution. It has the benefits of simplicity and high throughput.
A conventional wet etching process is shown in FIG. 1. It uses a loader 1, a plurality of process tanks, quick drain clean tanks, a dryer 8, and an unloader 9. The quick drain clean tanks here are QDR (quick down rinse) tanks. First, wafers are loaded by the loader 1 and clamped by a robot, and then sequentially soaked in and taken out from the process tanks and quick drain clean tanks in order to perform chemical reactions with chemical solutions. For example, wafers are put into a hydrogen fluoric acid (FF) tank 2. After a predetermined period, these wafers are taken out from tank 2 and put into QDR tank 3 to be washed by deionized water (DI water) to remove residual chemical solution. Then wafers are taken out from tank 3 and put into another process tank 4 with a chemical solution such as a mixture of sulfuric acid and hydrogen peroxide (SPM) or mixture of hydrochloric acid and hydrogen peroxide (HPM). If the chemical solution contains fluorine, it must be stored in a tank made of materials that resist strong acid and corrosion, such as polytetrafluorethylene. If the chemical solution does not contain fluorine, it can be stored in a tank made of conventional materials, such as quartz. As shown in FIG. 1, after being processed through HF tank 2, QDR tank 3, SPM tank 4, QDR tank 5, HPM tank 6 and QDR tank 7, the wafers are dried by a dryer 8, and then moved out to the next process stage by an unloader 9.
There are some deficiencies in the conventional wet etch process. For example, it requires many tanks, which take up considerable space. Moreover, too many wafer movement steps result in chuck miss, e.g. dropping of wafers, and induces formation of particles on the wafers. These deficiencies lead to defects and increased cost.